A section of pipeline that ruptured sending as much as 2,400 barrels of crude oil into the Santa Barbara coastline in May was severely corroded, federal regulators said on Wednesday.

Third-party inspectors estimated that corrosion of the line owned by Texas-based Plains All American Pipeline had degraded to 1/16th of an inch, said a U.S. Pipeline and Hazardous Materials Safety Administration (PHMSA) corrective action order document.

The May 19 spill dumped as much as 2,400 barrels (101,000 gallons or 382,000 liters) of crude onto a pristine stretch of the Santa Barbara coastline and into the Pacific, leaving slicks that stretched over 9 miles (14 km) along the coast and closing closed two California state beaches.

Fortunately, the spill was halted relatively soon after it began. The oil company said it shut the flow about 30 minutes after pressure irregularities were detected.

Two weeks before the spill, Plains All American Pipeline reported to the pipeline regulatory agency that the section of line where the rupture occurred had lost about 45 percent of its original wall thickness, the order said.

After the spill, third party inspectors estimated that corrosion at the site had degraded the wall thickness to an estimated 1/16 of an inch, which is greater than the 45 percent metal loss reported by Plains All American Pipeline, according to the order.

Inspectors also noted three repairs to the affected pipeline near the failure that were made due to external corrosion, the order said.

A U.S. Coast Guard captain overseeing the painstaking and arduous cleanup effort has said it may take months to restore the area to its natural condition.

The spill zone lies at the edge of a national marine sanctuary and state-designated underwater preserve teeming with whales, dolphins, sea lions, some 60 species of sea birds and more than 500 species of fish. The surrounding waters are shared by nearly two dozen offshore oil platforms.

On May 28, the U.S. Environmental Protection Agency (EPA) and the Coast Guard ordered the oil company to continue its efforts to clean up the pipeline breach and submit a written plan by June 6 that will outline measures for analyzing the spill’s effects on the environment.